
ALT The image illustrates different types of radio wave propagation based on frequency: H.F. (High Frequency) waves (blue lines) are shown reflecting off the ionosphere, allowing for long-distance communication (skywave propagation). V.H.F. (Very High Frequency) waves (red lines) are primarily line-of-sight and cannot penetrate the ionosphere, nor effectively go around large obstructions like mountains. U.H.F. (Ultra High Frequency) waves (green lines) are also line-of-sight and have similar propagation characteristics to VHF, generally passing through the ionosphere. The diagram demonstrates that lower frequencies (HF) can "skip" over obstacles by using the atmosphere's ionized layer, while higher frequencies (VHF and UHF) are blocked by terrain and require a clear path.





















